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Objectives learn how El Niño and La Niña work emphasize that the ocean & atmosphere are strongly coupled understand that one component of the Earth’s system can have drastic effects on the rest of the Earth

El Niño: The Enigma Unusual oceanic and atmospheric phenomenon - an anomaly We don’t know everything about it We can’t really predict it yet

El Niño: The Term First discovered in 1795 Recognized by local fisherman along Ecuador and Peru Warm, surface countercurrent North-->South Discovered around Christmas-time “The Christ Child”

El Niño Characteristics Normally develops in W. tropical Pacific Often results in natural disasters Occurs every 2 to 10 years Most recent and severe events in 1953, ‘57-’58, ‘65, ‘72-’73, ‘76-’77, ‘82-’83, ‘91-’92, ‘97-’98, ‘02-’04, ‘06-’07, ’09’10

Slides from 1982-’83 El Niño

-09-’10 INDEX = Air temperature Sea surface temp Surface winds Cloudiness of sky Sea level pressure -09-’10

Pressure!!

Suppressed Sea Surface Elevated Sea Surface

“Southern Oscillation” (SO) Tradewinds weaken or fail Tropical winds reverse and go east instead of west Atmospheric pressure cells reverse Wet areas become dry (drought) Dry areas get flooded “oscillates” like a giant sea-saw, taking 3-5 months

Non El Niño El Niño

Coupled Ocean-Atmosphere Circulation Non El Niño El Niño

Ocean’s Response to the SO Warm water moves to the east Elevates sea surface temperatures (SSTs) in SE Pacific Shuts down upwelling, can induce downwelling Reduces available nutrients Kills fish and sea birds - especially bad off Peru

Non El Niño El Niño

Animations

Ocean AND Atmosphere El Niño is both an oceanic and an atmospheric phenomenon Often called ENSO Scientists knew of SO from wind and precip. data Scientists knew of El Niño from SST data Didn’t make connection until 1969

Jacob Bjerknes Jacob Bjerknes, a Norwegian meteorologist made breakthrough in 1969 Combined wind, rain, AND SST data Ocean & atm. part of “big climate engine” Effects of ENSO not just local to Peru but could affect whole Pacific, whole world

Interdisciplinarity Rules! Bjerknes was a meterologist who was willing to take a good, hard look at oceanographic data Oceanography a versatile science

How Do We Track El Niño Today? in situ (on site) measurements Satellite sea surface temperature Computer models

Autonomous Temperature Line Acquisition System

Tropical Ocn Global Atm Tropical Atm-Ocn

La Niña NOT tied to the Southern Oscillation Tradewinds get stronger SSTs are lowered in SE Pacific Normal conditions are exaggerated Dry areas get drier (drought) Wet areas get wetter (floods) Occurs in between El Niños

INDEX = Air temperature Sea surface temp Surface winds Cloudiness of sky Sea level pressure

El Niño AND La Niña Both an ocean/atmosphere phenomenon Both affect wind, rain, and SST Both occur in cycles

More Animations

El Niño VERSUS La Niña “Southern Oscillation” Tradewinds fail Reverse flow of air Elevated SST Upwelling decreased Fish die Dry areas flood Wet areas dry up No oscillation Tradewinds increase No reverse flow Decreased SST Upwelling increased Fish thrive Dry areas get drier Wet areas flood

Lesson to be Learned Earth phenomena are very much interrelated Ocean <----> Atmosphere Bjerknes’ concept of “teleconnections” We must understand in order to predict Invest in soybean futures after an El Niño! No fish meal for cattle, farmers will use soy

We’re dealing with the interplay between two very different fluids - atmosphere and ocean - in the boundless dimensions of time and space. ... Abnormality in one causes abnormality in the other.... Events such as El Niños have no definite starting point and no end. It’s a matter of where you break into the scene, and where you leave it. Perhaps the only thing more complex is human behavior itself. -- Dr. Jerome Namias, Scripps Institution of Oceanography